A genetician has two banana flu populations in his laboratory. He looks at two c
ID: 211702 • Letter: A
Question
A genetician has two banana flu populations in his laboratory. He looks at two characteristics - the length of the hairline and the thickness of the wings. One population is homozygous for the dominant qualities thick and long, while the other is homozygous for the resilient properties thin and short.
(a) He performs a dihybrid crossing and follows the inheritance from the P to F2 generation. How is the distribution of the genotypes and phenotypes in F2?
(b) In addition to thickness and length, the two populations are homozygous for a third gene that
controls wing development. The population that is homozygous for thick wings and long
hairline is also homozygous for fully developed wings while the other population has
completely reduced wing development. Alleles that control wing development are incomplete dominant,
that is, heterozygous flies have the intermediate phenotype "short fingers" (neither
short or long wings). What is the likelihood that a fly in the F2 generation is thin
wings, long hair and short wings?
Explanation / Answer
A. AABB thick and long X aabb thin and short.
F1 AaBb thick and long
F2 9:3:3:1
AABB, AaBB, AABb, AaBb thick and long – 9 ; AAbb, Aabb thick and short – 3 ; aaBB, aaBb, Thin and long – 3; aabb thin and short. – 1
b. AABBCC thick and long and developed wings X aabbcc thin and short and reduced wing
F1 AaBbCc thick and long and short fingers
aaBBDd
aaBbDd
Genotype thin wings, long hair and short wings - aaBBCc and aaBbCc
Phenotypic ratio = 6/64 = 3/32
AB Ab aB ab AB AB AB AB AB Ab AB Ab AB Ab aB AB AB aB aB ab AB Ab aB abRelated Questions
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